that you fix with selling keys on the merchant, to those fsb/bsb/chest, with the stuff in you want to sell. Then seller dont need to be online.
You can even make the deal in pm and mail the key CoD and the buyer can go to you (or the place you placed the fsb/bsb/chest) and collect after he got the mail.
After "new" permissionsystem you only need key in inventory to be able to open the fsb/bsb/chest without owner set special permission.
But yah it seems you mostly want the stuff deliverd to your feet so you dont need to transport it yourself so then selling these keys dont help
But you in WU so im sure some great modder will be able to fix such I seen some stuff I really wanted on WO too